Check Digit on Sequences

This module extends the sequence configuration screen. When you open a sequence (for example under Settings > Technical > Sequences), a new field called check digit formula appears next to the implementation field. You can leave it as None or pick one of the standard formulas: EAN, Luhn, Damm, Verhoeff, or several ISO 7064 variants (Mod 11,2; 11,10; 37,2; 37,36; 97,10).

Once a formula is chosen, every number generated by that sequence automatically gets an extra check character appended at the end. The check character is calculated from the generated code itself, so the final number is longer than the raw sequence value.

• The module validates the formula together with the sequence prefix and suffix; if the combination cannot produce a valid check digit, Odoo shows the error "Format is not accepted" and refuses to save.
• If a formula is selected but is not implemented, a clear validation error is raised.
• The behaviour is applied at the moment the next sequence number is produced, so all documents using that sequence receive the check digit.

The module only touches the sequence model ir.sequence and its configuration view. It does not create new menus or reports. It is useful when numbers are read or typed manually, or exchanged with external systems, because a single wrong or swapped character makes the number invalid.